Multibranched Molecule Defoamers Based on Methyl Gallate for Highly Effective Defoaming and Antifoaming.

Bubbles or foams appear in many industrial processes, bringing inconvenience; yet, efficient capture or removal of them is still challenging. In this study, we report the synthesis and properties of multibranched molecule defoamers based on methyl gallate derivatives (Mb-GDs), which adopt methyl gallate (M-G) as the parent structure, by incorporating alkyl groups from alkyl isocyanates (A-I) with different chain lengths (C12 and C18) to replace R-OH in the M-G structure and further by linking two Mb-GDs into one Gemini-type multibranched derivative (Gt-Mb-GD) by transesterification to construct a defoamer material with a larger spatial volume. The surface properties and interfacial activity of molecular defoamers in aqueous solutions were studied, and the structure-property relationships of the multibranched gallate molecule defoamers based on Mb-GDs and Gt-Mb-GDs were further investigated by comparing the defoaming and antifoaming performance in four typical surfactant foams and foaming solutions with two kinds of commercial defoamers. The foam experiments indicated that the defoamers with a longer branched chain length (C18) showed more effectiveness in defoaming and antifoaming for four surfactant foams or foaming solutions, even at very low dosages, which were far stronger than the commercial high-carbon alcohol defoamer with a linear structure and comparable to branched silicone-based emulsion-type defoamers. Compared with Mb-GD defoamers, Gt-Mb-GD defoamers with a larger branched structure showed a higher defoaming performance. The study found the great potential of materials with multibranched structures for practical applications as the core components of high-performance defoamers.

Construction of high-branched derivatives based on melamine for highly effective defoaming and antifoaming.

Foams can be seen everywhere in human production and life. An uncontrolled foam event usually leads to product losses, equipment damage, and clean-up costs. Defoamer is one of the most effective strategies to eliminate or inhibit foam activities, which has been proved by long-term practices. In this work, we report new molecular defoamers with high-branched structure, which adopts melamine molecule as the parent structure, by incorporating alkyl-isocyanates with different chain lengths into the high-branched melamine derivatives (Hb-MDs) formula to replace the R - NH2 (primary ammonia) on melamine structure. The substitution reaction processes can be readily tuned by varying the molar ratio or alkyl chain length of alkyl-isocyanate, enabling a facile control over the branched degree. The foam tests reveal that the high-branched melamine molecule defoamers exhibited excellent defoaming and anti-foaming properties for four typical foam systems, including an anionic SDBS, cationic DTAB, non-ionic AEO-9, and white cat (BM) detergent, with efficiency close to that of silicone-type LN1414 defoamer and far superior to that of high-carbon alcohol XS-02 defoamer, at the same addition level. Notably, the defoaming or anti-foaming performances of the high-branched melamine molecule defoamers were not always monotonically increased with the branched degree or hydrophobic chain length, but a suitable range needed to be maintained to support a good balance of defoamer structure with foam liquid films. Therefore, it is anticipated that this high-branched design principle could open a new avenue for the construction of molecular defoamers for complex industrial problems.